Israeli Prime Minister Ariel Sharon has arrived in Washington for a critical meeting with President Bush Wednesday on his plan for "disengagement" from the Palestinians. On the eve of the meeting the Bush administration warmly welcomed his proposal for withdrawal from the Gaza strip, but was non-committal on his apparent aim to retain major settlement blocs in the West Bank.

The Bush-Sharon meeting was preceded by weeks of intensive consultations on the Sharon plan, which continued on the on the eve of the White House talks with a meeting between the Israeli leader and Bush National Security adviser Condoleezza Rice.

Mr. Sharon took the United States and other interested parties by surprise in February, when he said that in the absence of a Palestinian negotiating partner, he would embark on a unilateral plan for disengagement from the Palestinians, starting with the removal of Israeli settlements in the Gaza.

In weeks of talks with U.S. officials since then, Mr. Sharon is reported to have been seeking a set of at least implicit American assurances that under a final peace accord Israel could retain major settlement blocs in the West Bank and not be forced to withdraw to its pre-1967 boundaries.

The West Bank portion of Mr. Sharon's agenda has drawn Palestinian and other Arab criticism. But a news briefing, State Department spokesman Richard Boucher said the immediate prospect of an Israeli withdrawal from significant territory and the Palestinian administration of Gaza is an opportunity to move forward in the long-stalled regional peace process:

"I think it's a point that's often lost that we do see an opportunity here," he said. "We see an historic opportunity to move forward. The return of territory to Palestinian control is a significant development that we want to be able to take advantage of within the context of the 'road map' and the desire of all us to move forward towards the president's vision."

Mr. Boucher was not specific about what the Bush administration's response will be to Mr. Sharon's intentions regarding the West Bank, but he said the United States sees certain questions as "final status" issues that ultimately need to be negotiated between the parties.

In their meeting Monday in Texas, President Bush and Egyptian President Hosni Mubarak said that while an Israeli pullback in Gaza would be welcomed, it must be part of a wider agreement that would leave the Palestinians with a state.

Secretary of State Colin Powell spent much of Tuesday on the phone discussing the Middle East. He called U.N. Secretary-General Kofi Annan, Russian Foreign Minister Sergei Lavrov, and German Foreign Minister Joschka Fischer - all representatives of the diplomatic "quartet" that produced the Middle East road map early last year.

He also spoke to Jordanian Foreign Minister Marwan Muasher on the April 21 White House visit by Jordan's King Abdullah. Palestinian Foreign Minister Nabil Shaath is also due to meet Mr. Powell in Washington next week.